This invention deals with a method to measure the perfusion of the lungs in fluoroscopy in which it is possible to obtain the result as a numerical map which shows the perfusion normalised to the maximum value in the map.
Many different methods have been and are used to measure and evaluate different parameters of the function of the lungs. Methods possess considerable differences both in the performance and other factors like general requirements, pain and inconvenience to the patient, duration of the measurements, patient radiation dose.
Pulmonary embolism (PE) refers to the total or partial blockage of blood circulation in pulmonary arteries, and the seriousness is connected to the extend of the blockage. The diagnosis of PE is an important procedure in terms of the prognosis of the patient. An non-diagnosed PE may cause the death of the patient with the probability of about 30%, while when treated with anticoagulation it is 8%. Pulmonary embolism is, therefore, diagnosed based on the information obtained from nuclear medicine ventilation-perfusion scans, high resolution computed tomography HRCT or pulmonary angiography. The last method, pulmonary angiography is used to lesser extent due to its invasive nature and often poor availability. Scintigraphic ventilation-perfusion scans are most commonly used, but the interpretation of the examination may be ambiguous. The recently widely used method is CT imaging with contrast infusion in the spiral mode.
Information of different methods describe the lung function from different aspects, therefore different methods complement each other.
The goal of this invention is to set up a method in which a clear image is obtained of the conditions of lung perfusion. The examination is fast with no invasive interventions and with only a small radiation dose to the patient. The goal is achieved as is said to be characteristic to the invention in the accompanying claims.
The invention is described more accurately in the following using the enclosed drawings: